diff --git a/bin/update_homebrew.dart b/bin/update_homebrew.dart
index 691f0a5..68dc9e0 100644
--- a/bin/update_homebrew.dart
+++ b/bin/update_homebrew.dart
@@ -10,14 +10,17 @@
 
 void main(List<String> args) async {
   final parser = ArgParser()
+    ..addFlag('dry-run', abbr: 'n')
     ..addOption('revision', abbr: 'r')
     ..addOption('channel', abbr: 'c', allowed: supportedChannels)
     ..addOption('key', abbr: 'k');
   final options = parser.parse(args);
+  final dryRun = options['dry-run'] as bool;
   final revision = options['revision'] as String;
   final channel = options['channel'] as String;
   if ([revision, channel].contains(null)) {
-    print("Usage: update_homebrew.dart -r revision -c channel [-k ssh_key]\n"
+    print(
+        "Usage: update_homebrew.dart -r version -c channel [-k ssh_key] [-n]\n"
         "  ssh_key should allow pushes to $githubRepo on github");
     exitCode = 1;
     return;
@@ -46,8 +49,11 @@
         '-m',
         'Updated $channel branch to revision $revision'
       ], repository, gitEnvironment);
-
-      await runGit(['push'], repository, gitEnvironment);
+      if (dryRun) {
+        await runGit(['diff', 'origin/master'], repository, gitEnvironment);
+      } else {
+        await runGit(['push'], repository, gitEnvironment);
+      }
     } finally {
       await tempDir.delete(recursive: true);
     }
diff --git a/lib/src/impl.dart b/lib/src/impl.dart
index 2f7b66d..938108b 100644
--- a/lib/src/impl.dart
+++ b/lib/src/impl.dart
@@ -1,30 +1,23 @@
 part of '../update_homebrew.dart';
 
-const _files = {
-  'dev': [_x64Files, _ia32Files],
-  'stable': [_x64Files, _ia32Files]
-};
+const _files = [
+  'dartsdk-macos-x64-release.zip',
+  'dartsdk-linux-x64-release.zip',
+  'dartsdk-linux-arm64-release.zip',
+  'dartsdk-linux-ia32-release.zip',
+  'dartsdk-linux-arm-release.zip',
+];
 
-const _urlBase = 'https://storage.googleapis.com/dart-archive/channels';
-const _x64Files = {
-  'mac': 'sdk/dartsdk-macos-x64-release.zip',
-  'linux': 'sdk/dartsdk-linux-x64-release.zip',
-  'linux-arm': 'sdk/dartsdk-linux-arm64-release.zip',
-};
-const _ia32Files = {
-  'linux': 'sdk/dartsdk-linux-ia32-release.zip',
-  'linux-arm': 'sdk/dartsdk-linux-arm-release.zip',
-};
+const _host = 'https://storage.googleapis.com/dart-archive/channels';
 
 Future<String> _getHash256(
-    String channel, String revision, String download) async {
+    String channel, String version, String download) async {
   var client = http.Client();
   try {
     var api = storage.StorageApi(client);
-    var media = await api.objects.get('dart-archive',
-        'channels/$channel/release/$revision/$download.sha256sum',
+    var url = 'channels/$channel/release/$version/sdk/$download.sha256sum';
+    var media = await api.objects.get('dart-archive', url,
         downloadOptions: DownloadOptions.FullMedia) as Media;
-
     var hashLine = await ascii.decodeStream(media.stream);
     return RegExp('[0-9a-fA-F]*').stringMatch(hashLine);
   } finally {
@@ -32,138 +25,32 @@
   }
 }
 
-Future<String> _getVersion(String channel, String revision) async {
-  var client = http.Client();
-  try {
-    var api = storage.StorageApi(client);
-
-    var media = await api.objects.get(
-        'dart-archive', 'channels/$channel/release/$revision/VERSION',
-        downloadOptions: DownloadOptions.FullMedia) as Media;
-
-    var versionObject =
-        await json.fuse(ascii).decoder.bind(media.stream).first as Map;
-    return versionObject['version'] as String;
-  } finally {
-    client.close();
-  }
-}
-
-Future<Map<String, String>> _getCurrentRevisions(String repository) async {
-  var revisions = <String, String>{};
-  var lines = await (File(p.join(repository, dartRbFileName))).readAsLines();
-
-  for (var channel in supportedChannels) {
-    /// This RegExp between release/ and /sdk matches
-    /// * 1 digit followed by
-    /// * Any number of letters, numbers, dashes and dots
-    /// This covers both numeric- and version-formatted revisions
-    ///
-    /// Note: all of the regexp escape slashes `\` are double-escaped within the
-    /// Dart string
-    final regExp = RegExp('channels/$channel/release/(\\d[\\w\\d\\-\\.]*)/sdk');
-
-    revisions[channel] =
-        regExp.firstMatch(lines.firstWhere(regExp.hasMatch)).group(1);
-  }
-  return revisions;
-}
-
-Future<Map<String, Map>> _getHashes(Map<String, String> revisions) async {
-  var hashes = <String, Map>{};
-  for (var channel in supportedChannels) {
-    hashes[channel] = {};
-    for (var files in _files[channel]) {
-      for (var file in files.values) {
-        var hash = await _getHash256(channel, revisions[channel], file);
-        hashes[channel][file] = hash;
-      }
+Future<void> _updateFormula(String channel, File file, String version,
+    Map<String, String> hashes) async {
+  // Extract files and hashes that are stored in the formula in this format:
+  //  url "<url base>/<channel>/release/<version>/sdk/<artifact>.zip"
+  //  sha256 "<hash>"
+  var filesAndHashes = RegExp(
+      'channels/$channel/release' +
+          r'/(\d[\w\d\-\.]*)/sdk/([\w\d\-\.]+)\"\n(\s+)sha256 \"[\da-f]+\"',
+      multiLine: true);
+  var contents = await file.readAsString();
+  contents = contents.replaceAllMapped(filesAndHashes, (m) {
+    var currentVersion = m.group(1);
+    if (currentVersion == version) {
+      throw new ArgumentError(
+          "Channel $channel is already at version $version in homebrew.");
     }
-  }
-  return hashes;
+    var artifact = m.group(2);
+    var indent = m.group(3);
+    return 'channels/$channel/release/$version/sdk/$artifact"\n'
+        '${indent}sha256 "${hashes[artifact]}"';
+  });
+  await file.writeAsString(contents, flush: true);
 }
 
-String _createDartFormula(
-        Map revisions, Map hashes, String devVersion, String stableVersion) =>
-    '''
-class Dart < Formula
-  desc "The Dart SDK"
-  homepage "https://dart.dev"
-
-  version "$stableVersion"
-  if OS.mac?
-    url "$_urlBase/stable/release/${revisions['stable']}/${_x64Files['mac']}"
-    sha256 "${hashes['stable'][_x64Files['mac']]}"
-  elsif OS.linux? && Hardware::CPU.intel?
-    if Hardware::CPU.is_64_bit?
-      url "$_urlBase/stable/release/${revisions['stable']}/${_x64Files['linux']}"
-      sha256 "${hashes['stable'][_x64Files['linux']]}"
-    else
-      url "$_urlBase/stable/release/${revisions['stable']}/${_ia32Files['linux']}"
-      sha256 "${hashes['stable'][_ia32Files['linux']]}"
-    end
-  elsif OS.linux? && Hardware::CPU.arm?
-    if Hardware::CPU.is_64_bit?
-      url "$_urlBase/stable/release/${revisions['stable']}/${_x64Files['linux-arm']}"
-      sha256 "${hashes['stable'][_x64Files['linux-arm']]}"
-    else
-      url "$_urlBase/stable/release/${revisions['stable']}/${_ia32Files['linux-arm']}"
-      sha256 "${hashes['stable'][_ia32Files['linux-arm']]}"
-    end
-  end
-
-  devel do
-    version "$devVersion"
-    if OS.mac?
-      url "$_urlBase/dev/release/${revisions['dev']}/${_x64Files['mac']}"
-      sha256 "${hashes['dev'][_x64Files['mac']]}"
-    elsif OS.linux? && Hardware::CPU.intel?
-      if Hardware::CPU.is_64_bit?
-        url "$_urlBase/dev/release/${revisions['dev']}/${_x64Files['linux']}"
-        sha256 "${hashes['dev'][_x64Files['linux']]}"
-      else
-        url "$_urlBase/dev/release/${revisions['dev']}/${_ia32Files['linux']}"
-        sha256 "${hashes['dev'][_ia32Files['linux']]}"
-      end
-    elsif OS.linux? && Hardware::CPU.arm?
-      if Hardware::CPU.is_64_bit?
-        url "$_urlBase/dev/release/${revisions['dev']}/${_x64Files['linux-arm']}"
-        sha256 "${hashes['dev'][_x64Files['linux-arm']]}"
-      else
-        url "$_urlBase/dev/release/${revisions['dev']}/${_ia32Files['linux-arm']}"
-        sha256 "${hashes['dev'][_ia32Files['linux-arm']]}"
-      end
-    end
-  end
-
-  def install
-    libexec.install Dir["*"]
-    bin.install_symlink "#{libexec}/bin/dart"
-    bin.write_exec_script Dir["#{libexec}/bin/{pub,dart?*}"]
-  end
-
-  def shim_script(target)
-    <<~EOS
-      #!/usr/bin/env bash
-      exec "#{prefix}/#{target}" "\$@"
-    EOS
-  end
-
-  def caveats
-    <<~EOS
-      Please note the path to the Dart SDK:
-        #{opt_libexec}
-    EOS
-  end
-
-  test do
-    (testpath/"sample.dart").write <<~EOS
-      void main() {
-        print(r"test message");
-      }
-    EOS
-
-    assert_equal "test message\\n", shell_output("#{bin}/dart sample.dart")
-  end
-end
-''';
+Future<Map<String, String>> _getHashes(String channel, String version) async {
+  return <String, String>{
+    for (var file in _files) file: await _getHash256(channel, version, file)
+  };
+}
diff --git a/lib/update_homebrew.dart b/lib/update_homebrew.dart
index c2018d7..e38e51f 100644
--- a/lib/update_homebrew.dart
+++ b/lib/update_homebrew.dart
@@ -11,27 +11,19 @@
 
 const githubRepo = 'dart-lang/homebrew-dart';
 
-const dartRbFileName = 'dart.rb';
+const formulaByChannel = {
+  'beta': 'dart-beta.rb',
+  'dev': 'dart.rb',
+  'stable': 'dart.rb'
+};
 
-Iterable<String> get supportedChannels => _files.keys;
+Iterable<String> get supportedChannels => formulaByChannel.keys;
 
 Future<void> writeHomebrewInfo(
-    String channel, String revision, String repository) async {
-  var revisions = await _getCurrentRevisions(repository);
-
-  if (revisions[channel] == revision) {
-    print("Channel $channel is already at revision $revision in homebrew.");
-    exit(0);
-  }
-  revisions[channel] = revision;
-  var hashes = await _getHashes(revisions);
-  var devVersion = await _getVersion('dev', revisions['dev']);
-
-  var stableVersion = await _getVersion('stable', revisions['stable']);
-
-  await File(p.join(repository, dartRbFileName)).writeAsString(
-      _createDartFormula(revisions, hashes, devVersion, stableVersion),
-      flush: true);
+    String channel, String version, String repository) async {
+  var formula = File(p.join(repository, formulaByChannel[channel]));
+  var hashes = await _getHashes(channel, version);
+  await _updateFormula(channel, formula, version, hashes);
 }
 
 Future<void> runGit(List<String> args, String repository,